Quantifying nitrate dynamics in a mesotrophic lake using triple oxygen isotopes as tracers
Quantifying nitrate dynamics in a mesotrophic lake using triple oxygen isotopes as tracers
复制标题
使用三氧同位素作为示踪剂量化中营养湖中的硝酸盐动态
DOI：
10.1002/lno.10775
复制
发表时间：
2018
影响因子：
4.5
通讯作者：
Nakagawa Fumiko
中科院分区：
文献类型：
--
作者：
Tsunogai Urumu;Miyauchi Takanori;Ohyama Takuya;Komatsu Daisuke D.;Ito Masanori;Nakagawa Fumiko
在日本琵琶湖的中营养水体中，在1年的时间里，对硝酸盐的浓度和稳定同位素组成（包括17 O过量（Δ 17 O））的垂直分布进行了4次测定。通过使用大气硝酸盐在整个湖面上的沉积速率以及文献中报道的大气和矿化硝酸盐通过溪流的流入/流出，我们量化了硝酸盐的年动态（通过硝化作用的硝酸盐总生产率和通过同化和反硝化作用的硝酸盐总代谢率），以及它们的季节变化，基于Δ 17 O方法。结果表明，湖泊每年通过硝化作用向水体中提供642 ± 113 Mmol（Mmol = 106 mol）的硝酸盐，通过同化和反硝化作用向水体中提供810 ± 120 Mmol的硝酸盐。此外，该湖不仅在浅水层，而且在浅水层和温跃层上部也存在硝化作用。硝酸盐的总代谢率具有季节性变化，夏季最高，冬季最低。由于基于Δ 17 O方法估算的硝酸盐年代谢率与传统15 N培养法估算的硝酸盐年同化率之间的差异仅为20%，因此我们认为Δ 17 O方法可靠地估算了中营养湖泊中硝酸盐的动态。
Vertical distributions of both concentrations and stable isotopic compositions of nitrate, including the17O‐excesses (Δ17O), were determined four times during 1 yr within the mesotrophic water column of Lake Biwa in Japan. By using both the deposition rate of atmospheric nitrate onto the entire surface of the lake and the influx/efflux of both atmospheric and remineralized nitrate via streams reported in the literature, we quantified the annual dynamics of nitrate (gross production rate of nitrate through nitrification and gross metabolic rate of nitrate through assimilation and denitrification), together with their seasonal variations, based on the Δ17O method. The results revealed that 642 ± 113 Mmol (Mmol = 106mol) of the remineralized nitrate was supplied into the water column through nitrification in the lake on an annual basis, while 810 ± 120 Mmol of nitrate was metabolized in the lake through assimilation and denitrification. In addition, it turns out that nitrification was active, not only in the hypolimnion, but also in the epilimnion and upper thermocline in this lake. Furthermore, the total metabolic rates of nitrate varied seasonally, with the highest rates in summer and the lowest in winter. Because the difference between the annual metabolic rate of nitrate estimated based on the Δ17O method and the annual assimilation rate of nitrate estimated based on the traditional15N incubation method was only 20%, we concluded that the Δ17O method reliably estimates the dynamics of nitrate in mesotrophic lakes.